1. Field of the Invention
The present invention relates broadly to a device for extracting blood from a vessel, and, in particular, to a device for the extraction of arterial blood. Arterial blood sampling is recognized as an important diagnostic tool in the treating of patients suffering from lung or heart diseases in particular. In treating these patients, it is important to know the oxygen content of the blood. Oxygen content is determined through blood-gas analysis of arterial blood as opposed to venous blood. In the treatment of such patients, time may be of the essence and it is therefore desirable to have an arterial blood extraction device with which the physician or technician can immediately determine whether or not he is in fact extracting arterial as opposed to venous blood, and additionally such device should not be subject to atmospheric air contamination.
2. Prior Art
In the prior art, two devices and methods are typically utilized to extract arterial blood. One such method utilizes the conventional syringe with integral plunger and needle. The other conventional prior art method utilizes a vacuum container having one end which is punctured by one end of a needle, the other end of the needle being previously inserted into the artery.
With the conventional syringe in order to insure that arterial blood is being extracted, a relatively large size needle, i.e., a 20, 21 or 22 gauge needle, must be utilized. With such larger needles, the pressure of the arterial blood is adequate enough to push the syringe plunger allowing the syringe to fill spontaneously. If a smaller gauge needle, i.e., smaller than 22 gauge, is utilized with a conventional syringe, the blood pressure is inadequate to fill the syringe automatically and the physician or technician must utilize two hands to withdraw the blood. Since the blood does not fill the syringe spontaneously with the smaller needle, there is doubt as to whether or not the blood being extracted is in fact arterial blood. On the other hand, the larger size needles inflict more pain to the patient and it is more difficult to insert the larger size needle into the artery on the first attempt. There is a possibility with the larger size needle of greater damage or trauma to the artery and with the larger size needles part of the needle opening may be within the artery and part may be out of the artery resulting in blood escaping under the skin even while blood is being drawn. The larger size needle generates a larger wound and therefore the compression time to occlude the flow of blood after the extraction procedure is terminated is somewhat long (typically at least five minutes). Finally, an anti-coagulant (heparin) must be mixed with the blood to prevent clotting after the blood is drawn. In liquid form the heparin must initially be drawn into the syringe sufficient to coat the sides of the syringe prior to extracting the arterial blood.
The prior art method utilizing the vacuum tube eliminates the step of drawing liquid anti-coagulant since the interior of the vacuum tube is coated with a thin film of heparin. As previously mentioned, the vacuum tube is utilized in conjunction with a needle which is initially open to the atmosphere at both ends. One end of the needle is placed into the patient's artery. When the physician or technician visually sees blood through the other open end of the needle, the vacuum tube is then pushed over the open end of the needle puncturing the closure at one end of the vacuum tube and permitting the blood to enter the vacuum tube. When the tube is full, the needle must be withdrawn from the artery and a cork rubber stopper is placed over the needle to prevent air from entering the tube which would lead to an erroneous blood-gas analysis. The needle utilized with the vacuum container is typically the larger size needle having similar problems to those discussed above with respect to the syringe method. Additionally, in the vacuum tube method the physician or technician must use two hands to manipulate the tube over the needle to be pushed through the artery as the vacuum tube closure is being punctured. In the vacuum tube method the blood rapidly fills the vacuum tube regardless of whether or not the blood would be arterial or venous. Thus the vacuum tube has a significant problem of proper detection of arterial blood. It should be noted that detection by color is not always accurate. In the case of a patient having a low oxygen content in the blood the arterial blood will appear as very dark colored and similar to the color of venous blood in a person with a normal oxygen content. Vital time may be wasted if a blood sample is sent to the lab for analysis and the results indicate that the blood is venous blood. The treatment of acutely ill patients often depends on rapid and accurate determination of arterial blood-gas values. A delay of several minutes, which may not be uncommon in the prior art arterial blood extraction devices and methods may be critical to proper treatment.
Both prior art devices may be subject to air contamination during the extraction procedure. At times during the procedure the blood flow may stop indicating that the needle has somehow come out of the artery. The physician or technician must therefore probe in an attempt to reenter the artery. If during this attempt to reenter the artery, a portion of the needle bevel or opening comes out of the skin, air may enter the blood already extracted contaminating the blood and creating an erroneous blood-gas analysis.
The present invention overcomes the disadvantages of the prior art devices and methods in that it is an arterial blood extraction device which provides an immediate visual confirmation of arterial blood and which is adapted for use with a small size needle, i.e., 25 guage, that facilitates ease of entry into the artery and minimizes trauma to the artery and pain experienced by the patient. In the device of the present invention arterial blood is detected visually regardless of whether or not the patient has high or low arterial blood pressure. In the present device blood extraction can be terminated at any time during the procedure with the extracted blood sealed and thus not subject to air contamination. The arterial blood extraction device of the present invention can also be manipulated utilizing one hand thereby minimizing any movement of the needle once the needle is in position within the artery. Although the device of the present invention is designed in particular for arterial blood extraction it is to be understood that the device can also be utilized for venous blood extraction.